Single step stepping motor control

ABSTRACT

Nonoscillatory single step operation of a stepping motor is obtained by using the usual drive triggers to start the step operation, and using gating circuits therewith to obtain a one step-backward function logically from the trigger outputs and a Stop single shot for terminating the single step operation.

United States Patent Inventor Appl. No. Filed Patented Assignee SINGLESTEP STEPPING MOTOR CONTROL 3 Claims, 2 Drawing Figs.

US. Cl 318/696 1102 37/00 FieldofSearch 318/138, 254, 138 (A), 696, 685

24 26 28 30 0- 55 I SS I 1 [56] References Cited UNITED STATES PATENTS3,328,658 6/1967 Thompson 318/138 3,345,547 10/1967 Dunne 318/1383,386,018 5/1968 Smith-Vaniz... 318/138 3,423,658 l/l969 Barrus 318/1383,443,181 5/1969 Kozoletal 318/138 3,466,520 9/1969 Aylinkci et al318/138 Primary Examiner-G. R. Simmons Attorneys- Francis V. Giolma andl-lanifin and Jancin ABSTRACT: Nonoscillatory single step operation of astepping motor is obtained by using the usual drive triggers to startthe step operation, and using gating circuits therewith to obtain a onestep-backward function logically from the trigger outputs and a Stopsingle shot for terminating the single step operation.

Patented April 6, 1971 SS I 88 I +1 |-2Ms. v

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. SINGLE S'I'EPSTEPPING MOTORCONTROL FIELD OF INVENTION This inventionrelates generally to stepping motor control systemsandit'hasreference inparticular to a control system for obtaining nonoscillatory single stepoperation of a stepping motor.

DESCRIPTION OF THE PRIOR ART Heretofore, nonoscillatory single stepoperation of stepping motors has been effected by using bidirectionaltrigger rings and operatingthem to advance the ring one step at thestart of anincrement to accelerate the motor, retreating the ring onestep at the midpoint of the increment to decelerate the motor,

and then finally advancing thering one step to'hold the motor inits newposition.

.SUMMARY'OF THE INVENTION Generallystated, it is an'object of thisinvention to provide an-improved single step control system-for astepping motor.

More specifically, it is an object of this invention to provide forusing-a trigger ring to advance a stepping motor and to use logiccircuits therewith to gate the output of the ring to obtain a onestep-backward function without having to reverse the operation of thetriggers.

Another object of the invention is to provide for using a Stop singleshot to gate the outputs of a'pair of triggers for obtaining a onestep-backward output without having to reverse or effect furtheroperation of'the ring.

Yet another object of the invention is to provide a single stepoperating circuit for a stepping motor which utilizes a minimum ofcircuit components.

It is also an object of this invention to provide a simple and effectivecircuit for-effecting reliable, high speed, single step operation'of astepping motor in a carriage drive or the like.

It is also an object of the invention to provide for gating the outputsof a trigger ring to obtain a one step-backward function during aforward step of a stepping motor, so as to obtain fast and reliablenonoscillatory stepping motor operation without requiring the use ofexpensive bidirectional triggers.

In practicing the invention in one of its forms a pair of triggersareconnected in a gray code counter circuit to advance in response to aGO input signal, and control drivers for sequentially changing theconnections of the two phase windings of a stepping motor to effectenergization thereof to provide a one step-forward increment function. AStop single shot then gates the outputs of the triggers to provide forchanging the connections of the windings to effect a one stepbackwardfunction for decelerating the motor during the for ward increment,followed by a return to the original or normal step function connectionto hold the motor in itssingle step advanced position.

DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a schematic circuit diagram of a single step control circuitfor a stepping motor; and

FIG. 2 shows a plurality of timing curves and a displacement curveillustrating the operation of the circuit of FIG. 1 in controllingstepping motor for single step operation.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring particularly to FIG. Iof the drawing, the reference numeral denotes generally a cogtrolcircuit for a striping motor M having phase windings MA, MA, MB, and Mrespectively. The motor M may be generally of the type described inpaper 6 l-650 recommended by the AIEE Industrial 'Control Committee andpresented at the AIEE Northeastern District meeting, Hartford, Conn.,May 17-19, 196i, by Arthur E. Snowdon and Elmer W. Madsen, entitledCharacteristics of a Synchronous Inductor Motor, and in particular ofthe bifilar type shown in FIG. 10 of said paper.

The windings MA and MA are connected together at oneend, and areconnected by means of a resistor RAto one'terminal source. The otherends of the windings are connected by means for drivers A, A, B, and Bto the other terminals of, the source, comprising a pulse source suchas, for example, a pair of bidirectional switch devices such as triggersTA and TB,

which are connected in a well-known configuration to sequentiallyprovide dfiferent output levels to effect energization of the windingsMA, MA, MB, and MB ina well-known stepping manner is response to GOsignals, for example.

Instead of having the triggers TA and TB connected. directly to thedrivers, and connected to be driven eitherby feedback pulses or by aseparate pulse source such as an oscillator or the like, a plurality ofAND circuits l1, l2, l3, and 14 are used to gate the outputs of thetriggers TA and TB and apply the ou tputs thereof through OR circuits l6and 18 to the drivers A, A, B, and Bin conjunction with inverters 20 and22. A single shot 24 is provided for furnishing an output pulse of timedduration in response to GO signals for advancing the triggers foreffecting single step operation of the stepping motor M. The output ofthe single shot 24 is applied directly to the set and reset inputs ofthe triggers TA and TB, and is also applied through an inverter 26 to aStop single shot 28, which in conjunction with an inverter 30 providesgating signals for the outputs of the triggers TA and TB in the ANDs 11through -l4.

Referring to the circuit diagram of FIG. 1 in conjunction with thetiming chart of FIG. 2, with both the triggers TA and TB initially off,ANDs ll--l4 are off, as are ORs l6 and 1S Inverters 29 and 22 are on, sothat it will be seen that drive B. and drive A will be on, energizingthe motor windings MB and MA. When a G0 pulse occurs, single shot 24turns on to provide a pulse of predetermined timed duration. Thisadvances the triggers by turning on the trigger TA, being gated by theOFF output from trigger TB. Single shot 24 turning on, turns off theoutput of inverter 26. Inverter 26 being off, single shot 28 is off andthe output of inverter 30 is up. Since AND 11 responds to the outputs oftrigger TA and inverter 30, the output of AND 11 will rise. This causesthe output of OR 16 to rise, turning on driver A to energize the windingMA of the motor M and turning off the output of inverter 20 todeenergize driver A, commencing a one step-forward increment function ofthe motor M.

After an interval determined by the duration of the single shot 24,which can, for example, be on the order of 2 milliseconds, the outputpulse thereof terminates, and the output of the single shot 24 drops tozero. The output of the inverter 26 rises and fires the single shot 28,causing the output of the inverter 30 to fall. The output of the AND 11follows the output of the inverter 30 and falls to zero for the durationof the timing of the single shot 28, which can likewise have a durationon the order of 2 milliseconds. The output of the OR 16 follows theoutput of the AND 11, and falls, as does the output of the driver A. Theoutput of the driver A is the inversion of the output of the driver Aand rises. At the termination of the output from the Stop single shot 28the output of inverter 30 rises again. The output of AND 11 rises, asdoes that of OR 16. The output of driver A rises, and the output ofdriver A falls again. It will thus be seen that for a single GO pulsethe output of the driver A rose with the output of the single shot 24and fell with rise of the output of the Stop single shot 28, risingagain at the end of the OFF time for the inverter 30, to provide a onestep-forward function followed by a reverse or one stepbackward functionto decelerate the motor, followed by a return to the original onestep-forward function, thus effecting a nonoscillatory single stepoperation of the motor. The B driver remained off and the B driver on,for the duration of the described sequence.

With a subsequent or next GO pulse at some later time the single shot 24is again turned on, while the inverter 26 turns ofi, and the Stop singleshot 28 is turned on when the output of the inverter 26 again rises. Thetrigger TA remains on, and the trigger TB is turned on by the output ofthe single shot 24. This causes the output of the driver B to rise forthe duration of the output of the single shot 24, and to fall for theduration of the OFF interval of the inverter 30, at which time it risesagain to hold the motor in an advanced step position as shown by thetiming curves. The driver B follows the inversion of the driver B forthis sequence. 7

From the above description and the accompanying drawing it will be seenthat this invention provides a simple and effective single step controlcircuit for the stepping motor, which provides a forward step function,followed by a one stepbackward function while the trigger ring remainsin the forward step function condition, and a return to the originalforward step function condition, without requiring reversal of theoutput of the triggers. By utilizing logical AND circuits to gate theoutputs of the drive triggers TA and TB in the manner hereinbeforedescribed, a reliable and inexpensive nonoscillatory single step drivecircuit for a stepping motor is obtained. Complicated and expensivereversible triggers are not required, and the control circuit is greatlysimplified with a corresponding resultant reduction in the cost thereof.

lclaim: 1. In a control system for a stepping motor having a pluralityof pairs of separate phase windings:

bidirectional switch means comprising a pair of triggers each having ONand OFF outputs connected in a self-gating ring to provide a pluralityof output conditions for generating a sequence of output levels in apredetermined relation; circuit means including a plurality of ANDcircuits connecting said ON and OFF outputs of said triggers to saidpairs of windings, respectively, for energizing said windings inresponse to said levels in sequence to cause said motor to advance stepby step;

control means connected to said bidirectional switch means to apply asingle signal of timed duration thereto in response to an input signalto advance said bidirectional switch means from one operating conditionto another and produce a change in output level to cause the motor tocommence a one step-forward function; and

means including delay means comprising an inverter connected to invertsaid signal of timed duration and a single shot producing an outputpulse having a predetermined duration in response to rise of saidinverted input signal connecting said control means and said ANDcircuits operable to change the connections between said outputs of saidbidirectional switch means and said windings to provide a onestep-backward function for a predetermined time during said anotheroperating condition of the bidirectional switch means in response tosaid signal of timed duration, followed by a return to said onestep-forward function.

2. The invention as defined in claim 1 characterized by said circuitmeans comprising OR circuits connecting said AND circuits connected tosaid ON outputs to one pair of said windings, and connecting said ANDcircuits connected to said OFF outputs to the other of said pair ofwindings, and other inverter means connected in circuit relation betweeneach said OR circuit and a corresponding one of said pair of windings.

1. In a control system for a stepping motor having a plurality of pairsof separate phase windings: bidirectional switch means comprising a pairof triggers each having ON and OFF outputs connected in a self-gatingring to provide a plurality of output conditions for generating asequence of output levels in a predetermined relation; circuit meansincluding a plurality of AND circuits connecting said ON and OFF outputsof said triggers to said pairs of windings, respectively, for energizingsaid windings in response to said levels in sequence to cause said motorto advance step by step; control means connected to said bidirectionalswitch means to apply a single signal of timed duration thereto inresponse to an input signal to advance said bidirectional switch meansfrom one operating condition to another and produce a change in outputlevel to cause the motor to commence a one step-forward function; andmeans including delay means comprising an inverter connected to invertsaid signal of timed duration and a single shot producing an outputpulse having a predetermined duration in response to rise of saidinverted input signal connecting said control means and said ANDcircuits operable to change the connections between said outputs of saidbidirectional switch means and said windings to provide a onestep-backward function for a predetermined time during said anotheroperating condition of the bidirectional switch means in response tosaid signal of timed Duration, followed by a return to said onestep-forward function.
 2. The invention as defined in claim 1characterized by said circuit means comprising OR circuits connectingsaid AND circuits connected to said ON outputs to one pair of saidwindings, and connecting said AND circuits connected to said OFF outputsto the other of said pair of windings, and other inverter meansconnected in circuit relation between each said OR circuit and acorresponding one of said pair of windings connected thereto.
 3. Theinvention as defined in claim 2 characterized by said control meansincluding an additional inverter connected to said triggers and to saiddelay means for applying thereto a pulse of predetermined duration inresponse to said input pulse signal.